I don't see the problem with using the Arduino logo to "link" to the Arduino website,
although I might add the word Arduino next to it. Checking just one other place,
digikey does it too.
http://www.digikey.com/suppliers/us/arduino.page?lang=en
I might use their little blurb too,
Arduino - Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments.